And assuming you're not hiring as a drug test guinea pig, in which case it would actually matter, what's your basis for that? It has to be something a little more solid than "because George Bush said so".
I don't care what Bush said, it isn't relevant to me, however it is some how relevant to you.
A business owner is hiring, he risks his business, you risk nothing. If an accident happens, the liability is all on the owner, not the druggie. A druggie is more likely to steal, more likely to have an accident, more likely to have health issues, higher absentee issues. I am all for not hiring smokers. If you want to engage in high risk behavior, that is well within your rights, but an employer has rights to keep his business as low of risk as possible.